The present invention relates to an automatic transmission fluid (ATF) composition and continuously variable transmission (CVT) fluids containing the reaction product of a hydrocarbyl acrylate, or hydrocarbyl acrylamide, and a dihydrocarbyldithiophosphoric acid. More specifically, the present invention relates to ash-free lubricating oil compositions for power transmitting fluids that exhibit unusually high and durable torque capacity in friction tests. In one embodiment of the present invention there is a useful reaction product of C10 to C20 hydrocarbyl acrylate(s) with dihydrocarbyldithiophosphoric acids.
OEMs have adapted a variety of friction tests designed to identify ATFs that maintain their initial shudder-free performance at friction levels that translate to better fuel efficiency. Only a few fluids that are commercially available can meet current torque capacity and friction durability targets in specified durability tests.
U.S. Pat. No. 5,403,501 teaches lubricating compositions for manual transmissions comprising a phosphorous-containing compound.
Great Britain Patent Application No. 1569730A teaches a lubricating oil composition comprising the reaction product of an alcohol and P2S5 and ethyl acrylate.
U.S. Pat. No. 4,792,410 issued to Schwind et al. relates to lubricant compositions suitable for manual transmission fluids.
U.S. Pat. No. 4,744,920 issued to Fischer et al. relates to carbonated overbased products which are borated and processes for making the same.
U.S. Pat. No. 3,929,650 issued to King et al. discloses borated overbased alkali metal carbonates of metal sulfonates.
U.S. Pat. No. 3,480,548 issued to Hellmuth et al. discloses overbased boronated products.
U.S. Pat. No. 3,679,584 issued to Hellmuth relates to overbased alkaline earth metal sulfonates reacted with boric acid.
U.S. Pat. Nos. 4,119,549 and 4,191,659 issued to Davis and U.S. Pat. Nos. 4,119,550 and 4,344,854 issued to Davis et al. relate to sulfurized compositions prepared by the reaction of olefin compounds with a mixture of sulfur and hydrogen sulfide.
U.S. Pat. No. 5,354,485 teaches a composition comprising a major amount of an oil of lubricating viscosity, and an organic ammonium thiosulfate.
U.S. Pat. Nos. 5,464,548 and 5,484,542 also illustrate lubricating compositions containing sulfurized components.
An objective of this invention is to provide a power transmitting fluid that meets or exceeds the requirements of current friction performance tests in terms of both durability and torque capacity.
A feature of the present invention is to provide a lubricating oil composition containing an additive prepared from the reaction of a hydrocarbyl acrylate, or a derivative thereof, and a dihydrocarbyldithiophosphoric acid.
Another feature of the present invention is to provide a power transmitting fluid containing a reaction product produced by the reaction of a hydrocarbyl acrylate, or a derivative thereof, and a dialkyldithiophosphoric acid. By xe2x80x9cpower transmitting fluidxe2x80x9d herein is meant any fluid or composition useful for transmitting or conveying power or pressure, such as but not limited to hydraulic fluids, gear oils, ATFs and CVT fluids.
A further feature of the present invention is to provide a method of improving simultaneously the friction stability, durability, and torque capacity of a transmission fluid.
Accordingly, the present invention relates to an ash-free lubricating oil composition for power transmitting fluids including CVT.
According to an embodiment of the present invention, there is provided herein a clear superiority of lubricating and power transmitting oil compositions of the present invention over commercialy available oils optimized to provide friction stability and high torque capacity.
Static coefficient of friction measured as xcexcs and xcexct are particularly important in the commercialization of power transmitting fluids since automakers look at these parameters as a measure of torque capacity. In the present invention; by xe2x80x9cxcexcsxe2x80x9d is meant the static-coefficient of friction calculated by the formula 3.6.2 of JASO M 348-95 by the peak torque Ts after drag is started. By xe2x80x9cxcexctxe2x80x9d what is meant in the present invention is the static friction coefficient calculated by the formula 3.6.2 of JASO M 348-95 using the stable torque two seconds after dragging is started. By xe2x80x9cxcexc0xe2x80x9d what is meant herein is the dynamic friction coefficient calculated by 3.6.2 of JASO M 348-95 using the maximum torque on the completion of the stopping at 200 r/min, and by xe2x80x9cxcexcdxe2x80x9d what is meant herein is the dynamic friction coefficient calculated using friction torque at the time when the number of revolutions reaches 1800 r/min. Another key friction performance parameter is xcexc0/xcexcd, which is regarded as indicative of vehicle shudder characteristics of the fluid. The desired value of the xcexc0/xcexcd parameter is less than 1.0. The compositions of the present invention are better in this xcexc0/xcexcd parameter than that of a commercial power transmitting fluid that meets current durability requirements of Japanese OEMs. From this point on, this fluid will be cited as the reference fluid.
In the JASO M 348-95 test, the data is obtained using a paper-on-steel type of surface contact. The paper friction material used in the JASO test was SD-1777, available from Borg-Warner Automotive.
The power transmitting fluids of the present invention that are formulated containing the reaction products of hydrocarbyl acrylates with dihydrocarbyldithiophosphoric acids give unusually high xcexct and xcexcd levels in a SAE#2 machine when tested as taught in the JASO procedure cited above. The friction levels for power transmitting fluids of the present invention containing the reaction products described herein exhibit minimal variation during 5,000 cycles. The reference fluid shows a lower (unstable) level of xcexcd and much lower level of xcexct relative to the corresponding values for compositions of the present invention.
As an indicator of shudder performance, both the baseline fluid (i.e., no friction modifiers added) and reference oil show xcexc0/xcexcd greater than 1.0, while the same parameter for the ATFs and CVTs formulated with the compositions of the present invention provide xcexc0/xcexcd parameter values close to or below 1.0. For improved anti-shudder performance, a lower xcexc0/xcexcd parameter is desirable.
The present invention further relates to methods to improve the power transmission in vehicles by incorporation into the power transmitting fluid a power transmitting fluid composition of the present invention.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.